Good morning, everyone. I am a G.I.A. student trying to pass the 20-stone test. I keep missing 1, so that’s a failing grade. Inevitably, the misidentified stone relies on the ability to see doubling (I.e., zircon vs. some other clear stone). I have tried every strategy for seeing doubling (such as using a polarized filter) and I still have trouble distinguishing doubling from facet reflections or the switch from light to dark with the filter. When I look at internet & G.I.A. photos/videos of doubling, it’s obvious, but not in my test stones (to me, anyway). Any suggestions?
Also, is there somewhere that I could get a variety of OTL clear stones on which to practice (also that won’t cost me the proverbial arm and a leg).
Thanks in advance for any help you can give.